Front-end web developers face challenges when using common “asynchronous” requests. These requests, such as fetching a URL or reading a file, often lead to complicated code, especially when performing multiple actions in a row. How can we make this easier for developers?

Javascript Promises are a new tool that simplifies asynchronous code, converting a tangle of callbacks and event handlers into simple, straightforward code such as: fetch(url).then(decodeJSON).then(addToPage)...

We’ve just opened up a online course on Promises, built in collaboration with Udacity. This brief course, which you can finish in about a day, walks you through building an “Exoplanet Explorer” app that reads and displays live data using Promises. You’ll also learn to use the Fetch API and finally kiss XMLHttpRequest goodbye!

This short course is a prerequisite for most of the Senior Web Developer Nanodegree. Whether you are in the paid Nanodegree program or taking the course for free, won’t you come learn to make your code simpler and more reliable today?

Posted by Laurence Moroney, Developer Advocate
We’re delighted to announce the availability of Google Play services 8.4. There’s a lot of new information to share with you about what’s available to you in this release.

Custom Email App Invites

App Invites is a technology that enables your users to share apps with people they know. In Google Play services 8.4 we’ve updated this to make it easier for them to share via email. Before this you could create a custom email that contained user defined text and an image, but now we’re allowing you to add content from the app directly into the message. It allows you to fully define the email body using HTML, and set the email subject line. So, for example, if you have a favorite cooking app that you want to share with your friends, your invite to use the app can include a favorite recipe from the app. They get the immediate benefit of being able to access the desired content, giving them a more informed choice about whether or not they decide to install the app to get richer and more content. Check out the App Invites sample on GitHub here.

Predicting User spend and churn in games

The Play Games Analytics developer experience is designed to enable game developers to better understand, manage, and optimize game experiences throughout the player lifecycle. With this in mind, we’ve extended the Player Stats API to help you better understand your players behavior, and based on this, entice them to stay in your game.
The churn prediction method will return data on the probability that the player will churn, i.e., stop playing the game. You can create content in response to this to entice them to stay in your game.
Additionally, the spend prediction method will return the probability that the player will spend something in the game. It’s up to you how to handle this data, but -- for example -- if there’s a low probability that the player will spend something, you could provide discounted in-app purchases or show ads.

Fused Location Provider Updates

The Fused Location Provider (FLP) in Google Play services provides location to your apps using a number of sensors, including GPS, WiFi and Cell Towers.
When desiring to save battery power, and using coarse updates, the FLP doesn’t use Global Positioning Services (GPS), and instead uses WiFi and Cell tower signals. In Google Play services 8.4, we have greatly improved how the FLP detects location from cell towers. Prior to this, we would get the location information relative to only the primary cell tower. Now, the FLP takes the primary tower and other towers nearby to provide a more accurate location. We’ve also improved location detection from WiFi access points, particularly in areas where GPS is not available -- such as indoors.

Maps API Improvements

Have you ever wished you could easily handle a tap on a suburb without having to add another layer on the map to intercept the taps? We’ve added an onClickListener for polygons, so you can easily add transparent polygons and intercept the taps directly. We’ve also added on click listeners to polylines and ground overlays.
Here’s how you can use a listener to detect a click on a polygon:

For more details, and an example that uses these, see the ApiDemos sample on GitHub and check out the historical changes to this sample, so you can see how the new APIs work. Also see the Release Notes.

Support for Aztec bar codes

In Google Play services 7.8, we launched Vision APIs that supported face and barcode detection. One bar code format we didn’t support was Aztec bar codes, so with Google Play services 8.4 we’ve now added support for these.
Applications using BarcodeDetector in its default configuration (no barcode format restrictions) will automatically start decoding AZTEC codes.

Background Beacon Scanning

With Google Play services 8.4, the Nearby Messages API now supports background scanning for Eddystone, the open beacon format from Google. With this update, your app can be woken up when a BLE beacon is sighted. Back in July, Google Play Services 7.8 introduced the Nearby Messages API with a simple publish-subscribe interface. In the case of beacons, developers publish content by adding attachments to beacon records using Proximity Beacon API. These attachments are served back to your app when Nearby sights a beacon of interest.
New methods that we’ve added include a subscribe method for background beacon subscriptions where BLE scans are triggered at screen-on events; an associated unsubscribe event; and the ability to handle intents that you get when the Nearby API calls back during a background subscription.

Place Picker Autocomplete Widget

Today we are announcing the mobile autocomplete widget, the latest addition to our existing set of programmatic autocomplete features on Android and iOS, as well as the addition of Autocomplete to our place picker widget. Autocomplete functionality assists users by automatically completing the name and address of a place as they type. Widgets make it even easier for developers to add autocomplete functionality to their application with just a small amount of code. Learn more about this at this blog post.

Magic moments happen when your app does something very useful with minimal effort from your users -- like figuring out their location for them automatically. The new Places lesson in the Advanced Android App Development course teaches you how to add a Place Picker to your app so that users can pick a nearby location without having to type anything.

The Advanced Android App Development course, built by Udacity in conjunction with Google, is a follow-up course to Developing Android apps. The advanced course is for Android Developers who are ready to learn how to polish, productionize and publish their app, and even distribute it through Google Play.

Updates to the course also include an explanation of the new GCM Receiver, as well as an entirely new lesson on publishing your app, which explains how to build and sign an APK so you you can distribute your app on Google Play.

After all, why build an app if you can’t get it to your users?
Get started now, because it's going to be awesome!

The Holidays. Food for the body. Food for the mind. Google and Udacity offer you 31 courses that will make your mouth water and your mind dance. Savor one or several of our 31 self-paced online training courses to indulge your curiosity, expand your knowledge, and hone new skills. Choose from Android, Web, Entrepreneurship, or Cloud and Backend tracks. Are you ready?

Android

More and more people around the world are embracing mobile at an increasing pace, whether on their phones, in their cars, at home, and around their wrists. Learn to build apps for them!

Cloud and Backend

Does your app need to support more users? (Congratulations!) Do you want to move data handling for an existing app from the device to the cloud? Learn how to take advantage of public cloud infrastructure to support millions of users and terabytes of data.

During our recent talk at Android Dev Summit, we discuss the state of testing on Android on the example of a simple Notes application that we created as part of our testing codelab. In one section of the talk, we discuss the problem of test flakiness and introduce a simple solution for setting up a hermetic testing environment.

Combatting flaky tests

UI tests with frameworks like Espresso or UI Automator can easily get flaky if the application has external dependencies that can sometimes fail or take long to respond. In short, flaky tests are tests that are not reliable (they can pass or fail randomly) which defeats the whole purpose of having tests in the first place.

A common solution to this problem is hermetic testing or, in other words, making sure that your tests are isolated from dependencies. Using fake implementations or fake servers that just return predefined data is a common way of dealing with this problem. Here are some good examples:

Network calls can be made via a fake API client or fake server that immediately returns data from files stored on disk instead of hitting the network. This bypasses the network's latency and flakiness as well as any errors originating on the real server.

Interactions with low-level framework APIs (especially those for accessing hardware, like camera or storage) can be passed through an intermediate interface. A fake implementation of this interface could return immediately, providing a reference to preloaded data, such as an image, without relying on the hardware.

Any sensors can be replaced with fakes too: GPS, microphone, accelerometer etc., giving you a chance to test on data that would be difficult to provide for the test in real life, like a preset location or a set of inputs simulating a gesture.

Dependency Injection (DI) is a software design pattern that facilitates testing, reusing modules and making them interchangeable. DI frameworks can help you deal with the boilerplate associated with this pattern but it can take a considerable amount of time to set them up and understand how they work. Before you are ready to commit to one of those frameworks for your app, you might want to explore an easier way, especially if your project requirements are simple.

Managing dependencies with product flavors

Product flavors is a powerful feature of Android Studio and our Android Gradle plugin that lets you swap Java classes at compile time and doesn't require additional libraries. Some typical examples of flavor dimensions are:

free/paid flavors to generate two different APKs that will be released on your distribution channels

stable/experimental to keep experiments in a different source set and generate beta versions quickly

We can leverage the same mechanism to create two separate versions of our app to help with hermetic testing:

Create the class that you want to use for production code in the prod/java folder or move it from main/java. Make sure the main/java folder does not contain this class.

Create the same class (with the exact same class and file name) in the mock/java folder, but providing a different (fake) implementation that will be used for tests.

In the Build Variants window in Android Studio, choose the variant that you want to install or run tests against. A variant is the combination of a flavor and a build type.

Note: In gradle, the task names change when you add flavors. Instead of installDebug, you will now have to choose installProdDebug or installMockDebug.

Running your tests

With the prod and mock flavors configured and your mock implementation in place, you can now use the following gradle tasks to choose how your tests should run:

connectedMockDebugAndroidTest will merge the androidTest and androidTestMock directories and run every test found in the resulting source set. As these tests are run in a hermetic way, they will be faster and less flaky. This is ideal for a pre-submit check.

connectedProdDebugAndroidTest will use the real APIs and sensors so they might fail from time to time. If you have a Continuous Integration system, this task could be executed every night or used manually as a acceptance end-to-end test. Note that this task will run the tests in androidTest even if androidTestProd doesn't exist.

You can refer to our Android Testing Codelab to see how we used this method to provide different Injection class implementations, the one in prod providing real data and the other (mock) serving fake dependencies that use fake data for isolated test execution.

When you’re happy with your hermetic setup, you might want to give more flexibility to your build process and add even more dimensions to be able to interchange different components in your app. While the method discussed above is suitable for simple projects, for more complex situations it would be much better to invest some time to learn about and add a Dependency Injection framework to your project.

It’s been six months since the launch of Smart Lock for Passwords and we are thrilled with the impact it has made in getting users signed back in to many of their favorite apps. Million of users have been seamlessly signed in using saved accounts for over 40 major apps when going from one Android device to another or from Chrome to Android and vice versa. This first wave of developers have realized that removing the friction of sign-in increases user re-engagement, monetization opportunities, and cross-device analytics, improving the value and experience of their users.

The New York Times has seen 80 percent of their new sign-in events assisted by Smart Lock. Meanwhile, the Netflix customer support team found over a 20 percent reduction in support cases related to account recovery for their Android user base. Users strongly choose to stay signed in across their devices with over 60 percent opt-in to save sign-in info for major Smart Lock-enabled apps. And many of these developers were able to realize these gains with less than a day’s work by making only client-side changes to their app. To learn more about Smart Lock for Passwords, visit our developer site.

What’s New

With the latest release of Google Play services, we’ve made some enhancements to the Smart Lock for Passwords API to help you sign up new users or sign existing users in more quickly. Using the new method to retreive sign-in "hints", your users will see a dialog with a list of email addresses that they can select in a single tap:

This new experience is particularly important with Android Marshmallow’s runtime permissions model. To simplify and improve the user experience, this dialog doesn’t require device permissions and includes any email addresses that the user has saved with Smart Lock, not just the accounts on the device. This means that you can improve your sign-in and sign-up flows so that most of your users never need to type their email address. Apps using this dialog have seen nearly three-quarters of users select an entry shown, improving sign-up rates.

Next, after the user has tapped and shared their email address, with some server-side support, a sophisticated app can fully tailor the sign-in flow. By using the email address, you can check your database to see if a user has already registered for an account. You can then intelligently render either the sign-in or sign-up screens with the user’s email address, name and profile photo pre-filled.

Skipping the Password Altogether

It’s possible to do even better: if the user chooses a Google account from the dialog, an OpenID Connect ID Token is provided. This can save your app from having to verify email addresses for new accounts or skip the password altogether for returning users. ID tokens are also used by Google Sign-In to authenticate in place of a password, and are a strong assertion from Google that the owner of the given email address is present. If users on your site recover their passwords by email, then an ID token from Google is giving you the same assertion that the user owns the email address and is signed in to this device with that email address. You can also consider presence of ID token in addition to the password a signal to prevent password cracking and abuse.

We’ve found that the majority of users on Android use the email address that’s signed in on their device as their account for third-party apps, so this means seamlessly signing in most of your returning users, or creating a new account with one tap!

Code Samples and User Flow

Here’s a recap of how to streamline your app’s sign-in flow:

When your app starts, request stored Smart Lock credentials, and go straight to the user’s content when possible. Create a request for password or Google credentials, then listen for a callback with the results. Sign in immediately if stored user credentials (username / password, ID token, etc.) is available.

When the user wants or needs to sign in with their email address, show the picker to help them input it. Create a request for hints, pass control to the system to display UI, and handle the result when the user selects an entry.

The result from the hint request will contain the user’s selected identifier and an ID token if it is a Google account on the device. If you use the ID token, you must send and verify it on your server for security. Note that this token will also include a claim if the email address is verified, so you can skip any email verification step. If no token is present, or you can’t do server-side validation, just pre-fill the email field for the user.

On your server, after validating the ID token, use it to create an account or sign the user in without need for their password. Google provides libraries to do token validation, or you can use an open-source implementation. The ID token contains the user’s email address, and you can look it up in your database to determine whether an account needs to be created.

Then save the user’s email address credential “hint” in Smart Lock for automatic sign-in next time. Simply call the Credentials API save method with the hint and either set the user-entered password, or set the account type if you logged the user in with an ID token.

Credential credential = new Credential.Builder(hint)
// if you signed in with ID token,
// set account type to the URL for your app (instead of a password field)
//.setAccountType("https://yourdomain.com")
.setPassword(password)
.build();
Auth.CredentialsApi.save(mCredentialsApiClient, credential).setResultCallback(
new ResolvingResultCallbacks<Status>(this, RC_SAVE) {

Learn More

To learn more about the basics of a Smart Lock API integration, check out our code lab for a step-by-step guide. We’re excited to make authentication without passwords possible via Smart Lock and are looking forward to a world where not only credentials can be managed more effectively, but apps can get their users signed in and up quickly and securely without the friction of typing usernames and passwords. We’d love to hear your feedback or questions!

An early preview of the new Android Emulator is now available to try out. As a part of Android Studio 2.0, the latest version of the Android Emulator can help you test your app on a wide range of screens size and configurations beyond the physical Android hardware you use to test.Moreover, using the official Android emulator enables you to test with latest Android versions. Building on this foundation, the top two benefits of new Android emulator are:

Speed & Performance: When emulating the latest Android 6.0 release (Marshmallow), we now support Symmetric Multi-Processing and have made significant I/O improvements in both the emulator and ADB. This means you will have faster performance when you are testing your app.

Usability & User Interface: The new Android Emulator includes a brand new user interface to make the emulator easy to use. You no longer have to rely on command-line parameters to use the Android emulator. Common tasks and emulator features are now just a mouse click or a keyboard shortcut away.

We previewed the user interface at the Android Dev Summit. You can try it out today along with the new version of ADB for faster APK installation and file transfers to the emulator. Check out the video for a demonstration of the new Android Emulator.

Android Dev Summit 2015: Emulator Demo

We are seeking early feedback to continue to deliver the experience and features that will make you more productive.

Performance Improvements

CPU Performance

Android Studio now uses CPU acceleration on x86 emulator system images by default. Combined with new Symmetric Multi-Processor (SMP) support in Android 6.0 Marshmallow system images, the Android emulators can perform even faster than many physical Android devices. Multi-core support not only makes your apps and the emulator run faster but it provides the added advantage of speeding up common developer tasks such as installing APKs. Also, with SMP you can test apps that specifically target multi-processor Android devices.

Faster ADB

In addition to faster CPU speeds in the emulator, there are a number of under-the-hood improvements that will make the experience faster. One of the bottlenecks in the development process that we worked on is the speed of pushing data between Android Studio and your device using ADB (Android Debug Bridge). When you use Android 6.0 Marshmallow and higher system images with the new Android Emulator, you can now push files across ADB up to five times faster than a real device. This will help you if you push large APK or files during your app development cycle.

User Interface

Toolbar

The new interface exposes some of the most common emulator actions in a new toolbar and control panel instead of solely relying on command line options. For the preview, the Android Emulator toolbar enables actions, such as volume control, screen rotation, and screen-shots of the emulator window.

Window Zooming & Scaling

Now you can resize your window simply by dragging a corner. You can also zoom and scroll to get a closer look at a portion of your screen.

Left: Zooming

Right: Window Scaling

Drag & Drop

With the new emulator, you can not only drag and drop APKs for quick installation, but you can also drag and drop any file to your emulator’s internal SD card to help in testing.

Drag and Drop Files

Extended UI Controls

In the extended controls window, additional options help you validate and test features in your app. As shown below, you can initiate a range of emulator actions such as making a virtual call, sending a virtual SMS, or controlling the power level of the emulator. You can additionally send a single GPS location point to the emulator or play back a custom set of KML or GPX points as well.

Phone Controls

Battery Controls

We are continuing to add more functionality and we will keep you up to date as we add more features.

What's Next & Setup

This is just the beginning of developments on the Android Emulator, so expect more features such as support more APIs levels, and adding more sensors with future versions of Android Studio. The new emulator along with Android Studio are available today on the Android Studio canary channel and tools preview channel.

Click here for details on how to setup the preview of the new Android Emulator.

We appreciate your feedback. Connect with us, the Android Studio development team, on Google+.